The characteristics of a semiconductor, etc., such as an element having a multilayer structure in which many thin films are laminated on a substrate, vary according to the state of a film to be formed, such as the film thickness, density, crystalline, etc. of the film. Microfabrication and integration of these elements have recently progressed, and this tendency has become remarkable. Therefore, a thin film inspection device that is capable of accurately measuring the states of formed films have been required.
As this type of inspection device have been known direct measurement based on a cross-section transmission electron microscope (TEM), a film thickness inspection device using optical interference or ellipsometry, a photoacoustic device, etc. The present situation of the cross-sectional transmission electron microscope (TEM) is that it is impossible to install the cross-sectional transmission electron microscope in an in-line manufacturing process and inspect a thin film as an inspection target in real time, and also a product which is extracted for an inspection from the manufacturing line is discarded after the inspection. Furthermore, the film thickness inspection device using optical interference or ellipsometry and the photoacoustic device are suitable for the in-line process, but have insufficient precision for measurements of thin films of several nm.
Wafers for inspection which are discarded after used (blanket wafers) have imposed a large burden in cost on semiconductor device makers. Particularly, the diameter of semiconductor wafers has recently increased, so that the cost of one blanket wafer has also increased.